December 13, 2012

Protected by poison: ants disinfect the colony by using own toxin

IST Austria professor Sylvia Cremer’s publication in Current Biology identifies new disease defense mechanism in garden ants


Similar to monkeys delousing each other, ants lick the body surface of their nestmates or their brood to help keep them clean. This sanitary behavior of allo-grooming is an important mechanism to prevent disease breakouts in the colony. Grooming drastically lowers the number of infectious particles on the body of contaminated individuals and reduces their risk to fall ill.

In a publication in the current issue of Current Biology (Dec 13, 10.1016/j.cub.2012.11.034), the group of Prof. Sylvia Cremer at the Institute of Science and Technology Austria (IST Austria) has now uncovered that grooming also has a second function that so far has been overlooked: particles that cannot be removed from the body of exposed ants get disinfected by the chemical application of ant poison. It is known that garden ants spray their poison upon attacks by predators. The antimicrobial activity of the main component of the poison, formic acid, allows the ants to also use it in the secondary context of sanitation.

"To allow for accurate application of the poison on the contaminated nestmates, garden ants have evolved a novel sequence of behaviors: they first take up their own poison into the mouth and later apply it during grooming on the infected areas", explains Cremer. Whereas oral poison uptake may sound like a risky strategy, selfharm through the own poison is prevented by the lining of the mouth cavity with inert insect cuticle. Poison uptake therefore gives the secondary benefit that those infectious particles that actually are removed from the sick ants’ bodies and collected in the mouth of the cleaning ant can be disinfected and killed before being disposed of as a pellet in the corner of the nest.

The current study by the Cremer group at IST Austria highlights the sophisticated disease defense mechanisms of ant colonies taking place in our back yards; it also underlines the importance of the emerging field of Social Immunity as research area in order to unravel complex disease dynamics in social insect societies.

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